WASHINGTON — An airliner ran off a runway in Denver a year and a half ago because the flight's captain failed to use the plane's rudder to correct its direction during a strong crosswind, a federal safety panel said Tuesday.
The captain of Continental Airlines Flight 1404 stopped using the Boeing 737's right rudder about four seconds before a 52 mph gust hit the plane's tail. The wind caused the plane to "weathervane" – turn until its nose was pointed into the wind.
Contributing to the accident was the failure by the air traffic control system to provide the pilots with key wind information, and the airline industry's failure to incorporate high wind gusts into pilot training for takeoff in crosswind conditions, the board said.
The plane with 110 passengers and five crew members was in the midst of a takeoff roll at Denver International Airport on Dec. 20, 2008 when it suddenly veered left off a runway, rumbled across a frozen field, broke into pieces and burned.
No one was killed, but six people were seriously injured and dozens more were treated for minor injuries. Board members praised flight attendants for getting everyone off the plane before the fire entered the passenger cabin.
The board emphasized that although there was a brief moment in which the captain could have prevented the accident, he had several factors working against him. Most importantly, the board said that if the captain had been told by the air traffic controller who cleared the flight for takeoff that there had been guts as high as 46 mph recorded by one of two sensors closest to the runway, it's possible he would have waited until the wind had died down or requested a different runway.
The controller told pilots there was a crosswind of 31 mph. He didn't mention gusts. The reading was from the sensor closest to the departure end of the runway, which was the one controllers were instructed to use.
Continental's guidance to 737 pilots was not to take off in crosswinds exceeding 38 mph.
Board member Robert Sumwalt noted that winds elsewhere at the airport that day were much lighter, and that the plane that took off on the same runway immediately before Flight 1404 experienced no problems. Flight 1404 just happened to be going down the runway at the very instant there was an unusually strong gust.
"This was the perfect wind storm," Sumwalt said.
The captain had twice applied the plane's right rudder during the first 12 seconds of the takeoff roll to correct its direction back to the right. But when a gust caused the plane to swing violently to the left, he reached instead for the tiller, which turns the nose wheel and was of no use under the circumstances, investigators said.
Mike Wilson, a software developer from Boulder who was on the plane, said he still suffers from panic attacks whenever planes he's on hit turbulence or make rough landings.
"I'm not sure a 50 mph crosswind hitting the side of what would be the size of a barn door is recoverable," Wilson said of a gust hitting the side of the plane. "I'm not sure I agree with the idea that he (the pilot) could have kept it on the runway.
"I guess at the end of the day, any landing or aborted takeoff you can walk away from is a good one."
The captain had a lot of flying experience and a good safety record, but he had probably never encountered such strong crosswind during a takeoff. The board estimated pilots encounter crosswinds greater than 35 mph about once in 15,000 takeoffs.
Also working against the captain was Continental's flight simulator training for pilots. It included training for steady high crosswinds, but not for gusts, investigators said. Due to a quirk in the simulator's software, the airline thought pilots were being exposed to gusts, but didn't learn that wasn't the case until the NTSB's investigation, investigators said. They said that is probably the case at other airlines.
The board recommended that the Federal Aviation Administration require airlines to incorporate realistic, gusty winds into their pilot training.
The board also recommended the FAA conduct research on wind hazards at Denver and other airports downwind from mountains, and make that information available to pilots and controllers. NTSB also wants FAA to require controllers to give pilots more wind information when they have measurements from more than one source.
Windshear has long been a special concern at the 50-square-mile Denver airport, located on the plains just east of the Rocky Mountains. The airport has 32 strategically located wind sensors on airport grounds.
"In spite of what is perceived to be one of the best wind sensing systems in the country, things can still sneak through, and something did sneak through," said NTSB investigator Jack English.
Associated Press Writer P. Solomon Banda in Denver contributed to this report.
The National Transportation Safety Board http://www.ntsb.gov